Field of the Invention
The invention relates to the technology of an in-cell touch display, and more particularly to a driving method for an in-cell touch display and a mobile device using the same for solving the problem of the too long settling time upon switching between touch and display periods.
Description of the Related Art
In the existing architecture of an in-cell touch panel, a common voltage electrode VCOM required for the display panel is mainly divided into M×N small electrodes. Each small electrode may function as a touch sensor. Upon touch scanning, each display frame period is divided into several time slots. FIG. 1 is a timing chart showing an operation of a conventional in-cell touch display. As shown in FIG. 1, one frame period TFRAME is divided into time slots TP for touch sensors and time slots DP for display-scan. When the time slot TP for the touch sensor is converted into the time slot DP for display-scan, the common voltage electrode VCOM must have the direct current (DC) level (usually the negative voltage) due to the display-scan time. Therefore, all the small electrodes need to be charged to the negative DC voltage in the time slot DP for display-scan. At this time, the load to be driven by the touch drive circuit is the common voltage electrode VCOM of the overall touch display panel (M×N×each load of the electrode of the common voltage electrode VCOM). The above-mentioned load is relatively large, so the settling time (e.g., ST) for the common voltage electrode VCOM is usually not too short.
However, such driving method causes at least the following defects.
First, as the size of the in-cell touch panel is getting larger and larger, the total load for the common voltage electrode VCOM is getting higher and higher, and the settling time for the common voltage electrode VCOM is getting longer and longer. The display-processing drive integrated circuit needs more line buffers to perform the buffering to go through the settling time.
Second, as the screen resolution of the in-cell touch panel is getting higher and higher, the settling time for the common voltage electrode VCOM is not changed. However, the same settling time needs to correspond to more high-resolution display-scan lines, so that the larger line buffer is required to perform the buffering to go through the above-mentioned settling time. Thus, the area of the drive integrated circuit gets larger.